- The Penn Plax Therma-Temp Standing Thermometer is an all glass thermometer with a weighted base to keep it vertical as it bounces around your aquarium. Features a "safe zone" for most tropical fish. Features Weighted base for vertical alignment; "Safe zone" for most tropical fish; Helps you maintain a safe & comfortable environment for your fish; Contains no mercury.; Dimension - 3.1 L x 0.6 W x 7.4 H in.; Item Weight - 0.05 lbs.
Pen Plax Standing Thermometer